The purpose of this proposal is to assess the antiarrhythmic effects of n-3 polyunsaturated fatty acid (n-3 PUFA) dietary supplementation in patients who have survived ventricular tachycardia or fibrillation and have an implantable cardioverter defibrillator (ICD). The demonstration of a significant electrophysiologic and antiarrhythmic effect of an inexpensive and well tolerated dietary supplement in this high risk but relatively small subgroup would be a reason to consider a subsequent larger trial of dietary supplementation with n-3 PUFA for the primary prevention of sudden death in other high-risk populations.